1. Field of the Invention
The present invention relates to the field of displaying technology, and in particular to an organic light emitting diode (OLED) display device and a manufacturing method thereof.
2. The Related Arts
An OLED (Organic Light Emitting Diode) is a flat panel displaying technique of extremely prosperous future and it shows excellent displaying performance and also possesses various advantages, such as being self-luminous, simple structure, being ultra thin, fast response, wide view angle, low power consumption, and being capable of achieving flexible displaying and is thus regarded as a “dream display” and has attracted the attention of major display manufacturers and becomes the mainstream of the third-generation display devices of the field of displaying technology.
An OLED display device generally comprises a substrate, an anode formed on the substrate, an organic light emission layer formed on the anode, an electron transport layer formed on the organic light emission layer, and a cathode formed on the electron transport layer. In operation, holes from the anodes and electrons from the cathode are injected into the organic light emission layer. These electrons and holes are combined to become excited electron-hole pairs and the excited electron-hole pairs are converted from the excited state to the ground state for achieving illumination.
In a manufacture process of an OLED display device, to reduce the difficulty of the process and deterioration and inhomogeneity of color and brightness of luminescent materials, it is common to adopt a display method involving sub pixels of four colors including red (R), green (G), blue (B), and white (W) is commonly utilized. This is WRGB OLED displaying. The operation principle of WRGB OLED displaying is to utilize a white organic light emitting diode to emit white light and color filters to convert the white light into red light, green light, and blue light for providing an OLED display device with WRGB four color displaying.
As shown in FIG. 1, in a pixel structure of a conventional WRGB OLED, an organic light emitting diode used is a white organic light emitting diode that emits white light, while red, green, and blue sub pixels comprise filters 300 that respectively convert the white light into red light, green light, and blue light. A white sub pixel remains to emit white light and requires no filter 300. Thus, the layer where a white organic light emitting diode of the white sub pixel is formed is lower than the layer where an organic light emitting diode of the red, green, blue sub pixel is formed. Thus, a first electrode layer 100 of the white sub pixel is also lower than a first electrode layer 100′ of the red, green, or blue sub pixel. A vertical distance y1 between the first electrode layer 100 of the white sub pixel and bottom wiring 400 of the white sub pixel is smaller than a vertical distance y2 between the first electrode layer 100′ of the red, green, or blue sub pixel and the bottom wiring 400. Structures of the blue sub pixel and the white sub pixel are illustrated in FIG. 1 for explanation.
In an actual manufacturing process, introduction of impurity resulting from improper treatments (such as residue of photo resist, unclean etching) may easily cause influence on the white sub pixel of which the vertical distance between the bottom wiring 400 and the first electrode layer 100 is shorter, whereby shorting or over current may occur between the bottom wiring 400 and the first electrode 100 in an area 200 where the bottom wiring 400 and the first electrode 100 overlap each other.